Screen and frame structure with frame functioning as a torque tube



June 1955 B. ARMSTRONG SCREEN AND FRAME STRUCTURE WITH FRAME FUNCTIONINGAS A TORQUE TUBE Filed Jan. 16. 1955 INVENTOR. BRUCE HAW: mow B H 7.TORNA'Y United States Patent CREEN AND FRAME STRUCTURE WITH FRAMEFUNCTIONING AS A TORQUE TUBE Bruce Armstrong, Saginaw, Mich., assignorto Jackson & Church Company, Saginaw, Mich., a corporation of MichiganApplication January 16, 1953, Serial No. 331,633

4 Claims. (Cl. 100--117) This invention relates to screw type pressesand it relates particularly to the type thereof having a perforatedscreen surrounding a pressing spindle and an imperforate tubular housingsurrounding said screen, with said housing and screen so related to asupporting frame that the twisting force applied by the spindle to thescreen is transferred through a relatively small portion of the screenand, through the press structure to the bottom of the tubular housingand thence to the supporting frame. Thus, the greater part of the screenis free from any substantial torsional stresses and may be provided witha maximum of open area for effecting maximum drainage.

In the operation of conventional presses, it has frequently beenobserved that the material being pressed, in attempting to follow therotating spindle, exerts a strong drag on the screen which closelysurrounds the spindle, particularly at the lower end thereof, and saidscreen is thereby unduly twisted. Often said lower end actually becomescircumferentially displaced with respect to the other end of said screenand this may cause buckling or breaking of the screen.

This problem has been apparent in presses of this general type for agreat many years and thus far the remedies which have occurred to theindustry are (1) to design the screens of strength sufficient to enablethem to withstand the twisting forces applied thereto by the spindle,but this made them so heavy as to be extremely expensive .and also as toseverely limit the amount of open area which was supplied in the upperportion of the screen, (2) to apply to the outside of the screen areinforcing grill but this was also expensive and it provided a largearea over which material would sometimes gather and require cleaning andit further limited said open area, or (3) to so limit the supply ofmaterial to the spindle that it would not exceed the torsional strengthof the screen but this often improperly restricted the capacity of theapparatus.

Accordingly, it has long been desirable to provide a construction whichwould relieve a screen from the severe torsional stresses incident toprevious practice without the necessity of unreasonably limiting theoutput of the machine.

Thus, a major object of the invention is to provide a press in which thescreen may be of relatively light construction and have a large openarea therein without subjecting it to severe torsional stress ordisplacement.

A further object of the invention has been to provide a press, asaforesaid, in which practically the entire torsional load imposed ontothe screen by the rotation of the spindle is absorbed by an imperforatetubular housmg.

A further object of the invention has been to provide a press, asaforesaid, in which the tubular housing provided for absorbing thereaction to the rotation of the spindle is the same tubular housingwhich is placed radially outwardly of the screen for guiding expressedliquids downwardly.

A further object of the invention is a press, as afore- ICC said, whichwill accomplish the objects above named without departing materiallyfrom the present designs for the major parts thereof.

A further object of the invention is to provide a press, as aforesaid,in which the operation will not be materially different, excepting asindicated above, from the operation associated with present designs.

Other objects and purposes of the invention will be apparent to personsacquainted with apparatus of this general type upon reading thefollowing specification and inspecting the accompanying drawings inwhich:

Figure 1 is a central section of the lower part of said press.

Figure 2 is a central section of an upper part of said press.

Figure 3 is a sectional view taken along the line IIIIII of Figure 1.

Figure 4 is a fragmentary, sectional, view taken along the line IVIV ofFigure 2.

Figure 5 is a fragmentary, sectional, view taken along the line V-V ofFigure 1.

In accomplishing the objects and purposes above set forth, I have madeuse of the fact that the greater part of the reaction to the rotation ofthe screw occurs in the one third or one quarter of the press adjacentthe output end. Therefore, by holding the screen at its lower end onlyand permitting the upper end to move circumferentially, anycircumferential movement in the screen that takes place in response tothe rotation of the screw will impose an appreciable deforming forcethrough only a relatively short lower portion of said screen, whichportion needs relatively little open area and hence can be made verystrong, and thence said deforming force is conducted to the meansholding said lower end of the screen. Relatively little torsional stressis imposed on the upper two thirds to three quarters of the screen andhence this part can be designed with a maximum of open area. In thepresent preferred embodiment of the invention, I have mounted the lowerend of the screen rigidly onto the inner periphery of the usual liquidgathering trough, and have mounted the outer periphery of said troughrigidly onto the lower end of a coaxial, outwardly positioned, tubularhousing whose upper end is suspended rigidly from the mounting structureof the press. Thus, as the spindle rotates and the lower end of thescreen is urged to rotate in response to the frictional drag thereon bythe material being pressed, the forces are applied to the lower end ofthe screen which is rigidly attached as above indicated. Thus,essentially all the torsional twisting will take place in the tubularhousing only and this structure is such that it will be capable ofwithstanding the high torsional forces involved, and there will be nodamaging torsional stress on the screen.

For purposes of illustration, I have chosen a particular embodiment ofthe invention wherein the screen and screw portion of the press extendsdownwardly below the level of the floor to which this portion issecured, but it will be recognized that the principles of the inventionmay be applied where said screen and screw extend upwardly from amounting structure or, with slight modications, where said parts extendhorizontally. Therefore, for purposes of convenient reference in thehereinafter following description, the terms upper, upwardly, andderivatives thereof, and lower, below or downwardly, and derivativesthereof, will all be taken to refer to such directions when said machineis in its usual position of use, as shown, in which the axis ispositioned in a vertical direction, and the terms inward and outward,and derivatives thereof, will refer to directions toward and away fromthe central axis of the apparatus.

Turning to the drawing in more detail, an upper assembly 1, containingdrive mechanism not here shown, is mounted by a plate 2 onto an i-beamin a floor, or onto other suitable floor structure. Immediately belowsaid upper assembly is fastened a mounting member, here the ring 4 fromwhich is suspended the portion of the press with which the presentinvention is concerned.

Positioned immediately below said mounting ring 4 is a torque housingsupporting ring 6 which will be rigidly fastened to said ring 4 by anyconvenient means. From said ring 6 there is suspended a torque housing 7at the lower end of which is fastened a trough supporting ring, orflange, 8. A plurality of vertically positioned stiffening ribs, ofwhich one is indicated at 9, may be provided also if desired.

Suspended from said flange 8 is a trough 11 which trough may be of anyconventional construction, which in this instance is made of sheetsincluding an outer side 12 and inner side 13, a bottom 14, an outer rim15 and an inner rim 17. The lower housing flange S and the outer rim 16may be fastened together in any convenient manner.

A screen 18, in this embodiment comprising an upper section 19 a middlesection 20 and a bottom section 21, is supported upon a lower screenring 23, to which it is preferably welded, which in turn is supportedupon the inner rim 17 of the trough 11. Said lower screen ring 23 andsaid inner rim 17 are fastened together by any convenient means.Areinforcing structure 22 of any convenient type, here a fabricatedsteel frame, may be applied to said screen for stiffening same in anyconvenient manner. The upper end of the screen is affixed as by bolts 43to the ring 4, here through an intermediate ring 35, preferably througha pilot 25. The manner of such fastening is such as to permit limitedcircumferential movement, such as, for example, by passing saidfastening bolts 43 through elongated, circumferentially arrangedopenings 44 (Figure 4).

The screen 18 may be constructed in any of several ways. One preferredand novel way is illustrated in Figure 3. A cylinder 50 (only a sectionof which is shown), properly perforated and conveniently of steel plate,is machined accurately to size.

A backing screen 51 of relatively coarse mesh and of heavy stock, as M;inch thick perforated steel plate, is forced into place under sufficientpressure that it lies tightly against the cylinder 50. A relatively finemesh screen 52 is then placed against the screen 51 and its edges bentover at 53. Thus, the two screen members assume practically the exactcontour of the machined cylinder 50 and the inner surface of the innerscreen is thus positioned very accurately with respect to the flights ofthe spindle and very small clearances therebetween may be successfullymaintained. With the two halves of the screen structure fastenedtogether, the bentover edges of the inner screen will be firmly clampedin place.

The middle and upper sections 20 and 19 of the screen will be made withlarge open areas (Figure to permit free drainage while the lower section21 is made relatively heavy with somewhat less open area to provide thenecessary strength.

Resistors 54 are mounted in the frame structure and extend into thecompression space between the screen and spindle at such points withrespect to the flights on the spindle that they will not interfere withthe rotation of said spindle.

Simultaneously, the spindle 26 is rotated from its upper end by anyconventional mechanism, not shown. As theseveral flights 27 engage saidmaterial and force it downwardly through the progressively constrictingspace between said spindle and said screen, progressively greaterpressure is exerted onto said material and the liquid portion thereof isforced through the screen.' The re sistors 54 prevent the material frommerely traveling around with the spindle and insure efficient pressing.As said material approaches the lower end of said space and enters theportion thereof designated by the numeral 36, the friction between saidmaterial and the screen, and the drag of said material against theresistors, both become progressively greater and will tend to causerotation of said screen in the same direction as the rotation of saidspindle. Thus, it will be noted that most of said rotating effect isconcentrated at the lower end of said screen inasmuch as it is only atsaid lower end that said material is sufliciently compressed to cause asubstantial amount of frictional drag against the screen and issufficiently densified to engage the resistors with an appreciableeffect. Thus, with the greater part of the rotating forces applied tothe lower section 21 of said screen and transmitted downwardly throughthe trough to the housing 7, and the upper end of said screen free tomove in circumferential direction, the upper end of the screen willsubstantially follow whatever movement occurs at the lower end and therewill be no appreciable torsional stress on, or distortion of, theportion of said screen lying above the section 21 thereof.

The rotative force applied to said screen is transmitted to and throughthe trough 11 and thence to the lower end of the housing 7. Since thehousing 7 is rigidly affixed through the plate 4 to the base mounting ofthe device, it is fully able to withstand torsional stress placed at itslower end, and even if a certain amount of torsional displacement doesoccur, it will cause no harm.

Thus, since'the sections 19 and 20 will be subjected to relativelylittle torsional stress, it is possible to make them of lightconstruction and with large open areas, both of which features areconducive to efficient operation of the press.

Also, since relatively little liquid is expressed through the lowersection 21, it will be feasible to make this section with somewhat lessopen area and this will make possible a desirably strong structurewithout unduly restricting its eflicient operation. Further, since themajor torsional forces travel through only a short axial length of thescreen, even the lower section 21 may be of lighter construction thanwas required in previous designs.

Pressure fluid delivered from the source 42 through the conduit 41 intothe cylinder 39 will urge upward movement of the rod 37 which willthereby effect upward movement of the cone 33 toward the inner surface34 of the ring 23. By maintaining a constant pressure within thecylinder 39 the cone 33 will move upwardly or downwardly to compensatefor variations in the quantity of material delivered out from the lowerend of the chamber 36 at a given time between the cone 33 and ring 23.This will assure a constant pressure within said chamber 36 and aconstant consistency in the pressed solid material so discharged. Itshould be particularly noted, however, that the pressure imposed bysource 42 upon the cylinder 39 is of a dynamic nature so that a constantpressure is maintained at all times regardless of upward or downwardmovement of the rod 37 caused by variations in the quantity of materialdischarged from the chamber 36.

While the specific embodiment of the invention has been utilized hereinfor illustrative purposes, it will be recognized that many modificationsmay be made from said specific embodiment which will all lie within thescope of the appended claims and that said claims will accordingly coversaid variations excepting as said claims may by their own termsexpressly require otherwise.

I claim:

1. In a pulp press having a rotatable, tapered, spindle with radiallyextending, spirally arranged vanes positioned along the length thereofand a cylindrical perforated screen surrounding said spindle andpositioned coaxially with respect thereto, means for mounting saidscreen comprising: a non-rotatable mounting member; means engaging oneportion of said screen and supporting same on said mounting member, saidmeans permitting limited rotational movement of said screen around itsaxis with respect to said mounting member; a cylindrical imperforatehousing surrounding said screen and positioned coaxially therewith andaffixed rigidly to said mounting member; a liquid gathering troughrigidly afiixed both to said housing and to another portion of saidscreen, said other portion being spaced from said one portion; the pointof minimum clearance between said spindle and said screen being nearerto said other portion than to said one portion of said screen.

2. In a pulp press having a rotatable, tapered, spindle with radiallyextending, spirally arranged vanes positioned along the length thereofand a cylindrical perforated screen surrounding said spindle andpositioned coaxially with respect thereto, means for mounting saidscreen comprising: a non-rotatable mounting member; means engaging theupper end of said screen and supporting same from said mounting member,said means supporting the weight of said screen but permitting limitedrotational movement of said screen around its axis with respect to saidmounting member; a cylindrical imperforate housing surrounding saidscreen and positioned coaxially therewith and affixed rigidly to saidmounting member; a liquid gathering trough aflixed to the lower ends ofsaid casing and of said screen and fastened rigidly with respect to eachthereof; the point of minimum clearance between said spindle and saidscreen being adjacent the lower end of said screen.

3. In a pulp press having a rotatable, tapered, spindle and a screensurrounding said spindle, means for supporting said screen comprising incombination: a mounting member; means affixing one end of said screen tosaid non-rotatable mounting member and permitting limited movement ofsaid screen around its axis and with respect to said mounting member; animperforate cylindrical housing surrounding said screen and having theend thereof adjacent said one end of said screen aflixed immovably tosaid mounting member; means atfixing the other end of said housingimmovably with respect to the other end of said screen; said spindlebeing so tapered that the point of minimum clearance between spindle andsaid screen is adjacent said other end of said screen.

4. In a pulp press having a rotatable, tapered, spindle with radiallyextending, spirally arranged, vanes positioned along the length thereofand a cylindrical perforated screen surrounding said spindle andpositioned coaxially with respect thereto, means for mounting saidscreen comprising: a non-rotatable mounting member; means engaging theupper end of said screen and afiixing same to said mounting member, saidmeans supporting the weight of said screen but permitting limitedrotational movement of the top of said screen around its axis withrespect to said base; a cylindrical irnperforate housing surroundingsaid screen and positioned coaxially therewith and affixed rigidly tosaid mounting member; a circular trough and means affixing its radiallyouter rim rigidly to the lower end of said housing and other meansafiixing its radially inner rim rigidly to the lower end of said screen;the point of minimum clearance between said spindle and said screenbeing adjacent the lower end of said screen.

References Cited in the file of this patent UNITED STATES PATENTS797,374 Roberts Aug. 15, 1905 816,446 Fiddyment et a1 Mar. 27, 19061,598,818 Happensack Sept. 7, 1926 2,246,045 Hirschberg June 17, 19412,399,710 Schock May 7, 1946

